Oven and Forced Convection Continuous Tumble (FCCT) Roasting: Effect on Physicochemical, Structural and Functional Properties of Wheat Grain

Abstract

Wheat roasting is generally performed to enhance organoleptic properties of the end product, however, often with an inevitable effect on quality. This study investigated the physicochemical, structural and functional properties of the flour and whole wheat kernels after being roasted at 180 °C for 140 s using a conventional oven and a homogeneous and energy-efficient forced convection continuous tumble (FCCT) roaster. Wheat kernels tend to puff upon roasting, resulting in a significant (p ≤ 0.05) decrease in weight, bulk density, moisture content, flour yield, protein content and hardness for both roasting methods. FCCT roasting uses superheated steam instead of dry heat, which explains the lower weight loss with this roasting method compared to oven roasting. Scanning electron microscopy (SEM) demonstrated the minor influence of FCCT roasting on kernel structure. The structural changes, although not significantly different (p > 0.05), impacted on the degree of gelatinisation (FCCT = 10.14%; oven = 17.16%). Rheological characteristics, measured with an alveograph, were not affected (p > 0.05) by either roasting methods, whereas the peak time, measured with a mixograph, increased significantly (p ≤ 0.05) for both. The roasting conditions used did not result in a detrimental effect on the potential bread baking quality and may, in addition, delay staling with subsequent extension of shelf life. Further work is required to evaluate the quality and shelf life of baked products made with flour milled from roasted wheat kernels.